1. Technical Field
The present invention relates to a transfer-molding die structure, a transfer molding apparatus, a transfer molding method, an optical member, an area light source device, a liquid crystal display device, and a mobile device.
2. Related Art
Conventionally, for example, Japanese Unexamined Patent Publication No. 2005-310286 discloses a transfer-molding die structure, which is incorporated in an optical-product transfer molding apparatus. The optical-product transfer molding apparatus heats and pressurizes a resin film between a first die and a second die using a transfer plate to perform the transfer molding of a finely irregular pattern. The optical-product transfer molding apparatus includes: the transfer plate that includes a transfer surface used to perform the transfer molding to a transferred portion of the resin film; an elastic plate that presses a peripheral portion located around the transferred portion of the resin film; and a transfer-plate heating mechanism and a transfer-plate cooling mechanism, which are provided in at least one of the first die and the second die.
However, in the conventional die structure, it takes a long time to remove a bubble generated in the transfer molding. Particularly, in the case that a projecting portion is formed in the surface of the resin sheet, a large amount of air remains in a recess, which is provided in the transfer plate (a transfer member) in order to form the projecting portion, and it takes a longer time to remove a residual air, which degrades productivity.
As illustrated in FIG. 8A, in the case that plural arc regions (a bold dotted line) including tapered surfaces are continuously arrayed in an inner edge portion of the recess of the transfer member, a flow rate of a molten resin is not homogenized. Therefore, a region of fast flow rate of the molten resin differs from a region of slow flow rate of the molten resin in a deformation amount of the residual air (a bold solid line), and the residual air is deformed from an even width to different shapes (FIGS. 8B to 8E). As a result, as illustrated in FIG. 8F, a boundary bubble that is generated by separating part of the residual air remains in a molding product to degrade a yield ratio.